BLB Recon Turbo lack of low rpm boost

[rtommo]

Hi
I own a A4 Avant with the BLB engine that recently had a big failure of the turbo which snapped the impeller shaft.
Knowing that these engines suffer from oil pump issues i stripped the bottom half down to see if there was the usual chain/hex drive failures only to find that it was still working but the hex keyway to balance shaft was very worn but still not spinning in the shaft.
I decided to replace the complete balance shaft module with a modified drive unit (oversize hex) and fit the modded gears in place of the chain as the chain at 150000 Mls was rattly but still functional.
I sent the turbo for rebuild to Midland turbo who set it up and calibrated before i refitted to the engine that i also fitted with a new water pump and drive belt.
I have taken all precautions to make sure the turbo was primed correctly and all pipes were clean and clear before starting the engine.
Upon test driving for the first time after rebuild i got about 1 mile before code P0299 (boost pressure regulation control not reached) flagged up on the MIL.
I reset and cleared the code and no more codes have flagged up but i do have a noticeable lack of power now with boost below 2000 rpm but turbo boost kicks in at around 2000rpm.
My fuel consumption has also dropped from around 43 mpg to around 36 mpg
Before the turbo blew it was and has always (for the last 10 yrs) ran very well with loads of power/boost low down.
My question is does anyone have knowledge or a possible answer to the cause of this lack of low down boost.
Could it be an incorrect actuator rod length?
Thanks in advance!

[niall campbell]

have you rechecked the timing for the chain ?

is the EGR working …………… vacuum working ?

[rtommo]

I have deleted the balance shaft chain/sprockets and fitted a later gear driven balance shaft module with new intermediate gear.
Having changed the timing belt it was timed up with the locating pegs to camshafts and crankshaft at TDC (with a timing kit) so no issues here.
The EGR was and is still working fine and passes with no fault codes and i have checked all the vacuum lines and replaced N75 solenoid to be assured it wasn't faulty.
The car just seems to spool up noticeably slower below 2000rpm and at higher revs and when loading and changing gear it is very laggy on the throttle response.
I have checked the actuator with a vacuum gauge hand pump and it starts to move at around 6"hg and hits the stop at around 21"hg.
I was under the impression that this was satisfactorily set up?

[Crasher]

Midland Turbo are across the car park from our local TPS and only a mile ish from my house, they rebuild ALL my turbo’s which is about 1 a week and they NEVER make mistakes, their last ten year track record is 100% perfect, to be honest I have never dealt with another company who are so good, they have a Q5 2L TDI turbo of mine up there at the moment and they won’t guarantee the rebuild of the unit until we have found the underlying issue which caused it to self destruct which we will get on with tomorrow by dropping the sump.

Your fault code is indicative of a vacuum control system plumbing error.